Tissue factor is produced and released by endothelial cells soon after injury and is important in the initiation of the coagulation cascade. It is unclear if elevated temperatures, associated with febrile illness, can affect tissue factor expression. In this study, we examined the expression of tissue factor by human endothelial vein cells (HUVECs) during heat shock. HUVECs were exposed to 44C heat shock for 0, 1, 2,4, or 8h. Tissue factor and heat shock protein 72-specific mRNAs were detected using ribonuclease protection assay at 1, 2,4, or 8h of heat shock. Heat shocked HUVECs express elevated levels protein 72 specific mRNA which peaked at 2 hours. Tissue factor specific mRNA was upregulated in unshocked HUVECs in response to LPS. However heat shocked HUVECs expressed reduced levels of TF mRNA in response to LPS during heat shock. These qualitative data suggest that transcriptional regulation in HUVECs differs for heat shock protein and tissue factor mRNA in response to heat shock. Regulated expression of tissue factor is affected by heat shock. Key words: wound healing, endothelial cell, differential display, infective endocarditis